Attempts to seal cracks in the shaft of the Pike River Mine, so it would be safer to enter, have been delayed again.
Police say that sealing gaps in the slimline shaft with a foam product will prevent the escape of neutralising gases.
Crews have been trying to seal the cracks since the weekend, when dangerously high gas levels led to their evacuation from the site.
They were preparing to finally use a sealant at 1pm on Tuesday, when gas levels climbed again, and they had to leave the hillside.
The GAG machine, which is being used to neutralise gases in the mine, has been off since about 4pm on Monday. It is being rested regularly to prolong its useful lifespan.